/*
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

/* zstd_decompress_internal:
 * objects and definitions shared within lib/decompress modules */

#ifndef ZSTD_DECOMPRESS_INTERNAL_H
#define ZSTD_DECOMPRESS_INTERNAL_H

/*-*******************************************************
 *  Dependencies
 *********************************************************/
#include "mem.h"           /* BYTE, U16, U32 */
#include "zstd_internal.h" /* ZSTD_seqSymbol */

/*-*******************************************************
 *  Constants
 *********************************************************/
static const U32 LL_base[MaxLL + 1] = {
    0,     1,     2,     3,     4,      5,      6,      7,      8,
    9,     10,    11,    12,    13,     14,     15,     16,     18,
    20,    22,    24,    28,    32,     40,     48,     64,     0x80,
    0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000, 0x8000, 0x10000};

static const U32 OF_base[MaxOff + 1] = {
    0,          1,         1,         5,         0xD,       0x1D,
    0x3D,       0x7D,      0xFD,      0x1FD,     0x3FD,     0x7FD,
    0xFFD,      0x1FFD,    0x3FFD,    0x7FFD,    0xFFFD,    0x1FFFD,
    0x3FFFD,    0x7FFFD,   0xFFFFD,   0x1FFFFD,  0x3FFFFD,  0x7FFFFD,
    0xFFFFFD,   0x1FFFFFD, 0x3FFFFFD, 0x7FFFFFD, 0xFFFFFFD, 0x1FFFFFFD,
    0x3FFFFFFD, 0x7FFFFFFD};

static const U32 OF_bits[MaxOff + 1] = {
    0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10, 11, 12, 13, 14, 15,
    16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31};

static const U32 ML_base[MaxML + 1] = {
    3,     4,     5,     6,      7,      8,      9,      10,     11,
    12,    13,    14,    15,     16,     17,     18,     19,     20,
    21,    22,    23,    24,     25,     26,     27,     28,     29,
    30,    31,    32,    33,     34,     35,     37,     39,     41,
    43,    47,    51,    59,     67,     83,     99,     0x83,   0x103,
    0x203, 0x403, 0x803, 0x1003, 0x2003, 0x4003, 0x8003, 0x10003};

/*-*******************************************************
 *  Decompression types
 *********************************************************/
typedef struct {
    U32 fastMode;
    U32 tableLog;
} ZSTD_seqSymbol_header;

typedef struct {
    U16 nextState;
    BYTE nbAdditionalBits;
    BYTE nbBits;
    U32 baseValue;
} ZSTD_seqSymbol;

#define SEQSYMBOL_TABLE_SIZE(log) (1 + (1 << (log)))

typedef struct {
    ZSTD_seqSymbol LLTable[SEQSYMBOL_TABLE_SIZE(
        LLFSELog)]; /* Note : Space reserved for FSE Tables */
    ZSTD_seqSymbol OFTable[SEQSYMBOL_TABLE_SIZE(
        OffFSELog)]; /* is also used as temporary workspace while building
                        hufTable during DDict creation */
    ZSTD_seqSymbol MLTable[SEQSYMBOL_TABLE_SIZE(
        MLFSELog)]; /* and therefore must be at least
                       HUF_DECOMPRESS_WORKSPACE_SIZE large */
    HUF_DTable hufTable[HUF_DTABLE_SIZE(
        HufLog)]; /* can accommodate HUF_decompress4X */
    U32 rep[ZSTD_REP_NUM];
} ZSTD_entropyDTables_t;

typedef enum {
    ZSTDds_getFrameHeaderSize,
    ZSTDds_decodeFrameHeader,
    ZSTDds_decodeBlockHeader,
    ZSTDds_decompressBlock,
    ZSTDds_decompressLastBlock,
    ZSTDds_checkChecksum,
    ZSTDds_decodeSkippableHeader,
    ZSTDds_skipFrame
} ZSTD_dStage;

typedef enum {
    zdss_init = 0,
    zdss_loadHeader,
    zdss_read,
    zdss_load,
    zdss_flush
} ZSTD_dStreamStage;

typedef enum {
    ZSTD_use_indefinitely = -1, /* Use the dictionary indefinitely */
    ZSTD_dont_use = 0, /* Do not use the dictionary (if one exists free it) */
    ZSTD_use_once = 1  /* Use the dictionary once and set to ZSTD_dont_use */
} ZSTD_dictUses_e;

struct ZSTD_DCtx_s {
    const ZSTD_seqSymbol* LLTptr;
    const ZSTD_seqSymbol* MLTptr;
    const ZSTD_seqSymbol* OFTptr;
    const HUF_DTable* HUFptr;
    ZSTD_entropyDTables_t entropy;
    U32 workspace[HUF_DECOMPRESS_WORKSPACE_SIZE_U32]; /* space needed when
                                                         building huffman tables
                                                       */
    const void* previousDstEnd;                       /* detect continuity */
    const void* prefixStart;  /* start of current segment */
    const void* virtualStart; /* virtual start of previous segment if it was
                                 just before current one */
    const void* dictEnd;      /* end of previous segment */
    size_t expected;
    ZSTD_frameHeader fParams;
    U64 decodedSize;
    blockType_e
        bType; /* used in ZSTD_decompressContinue(), store blockType between
                  block header decoding and block decompression stages */
    ZSTD_dStage stage;
    U32 litEntropy;
    U32 fseEntropy;
    XXH64_state_t xxhState;
    size_t headerSize;
    ZSTD_format_e format;
    const BYTE* litPtr;
    ZSTD_customMem customMem;
    size_t litSize;
    size_t rleSize;
    size_t staticSize;
    int bmi2; /* == 1 if the CPU supports BMI2 and 0 otherwise. CPU support is
                 determined dynamically once per context lifetime. */

    /* dictionary */
    ZSTD_DDict* ddictLocal;
    const ZSTD_DDict* ddict; /* set by ZSTD_initDStream_usingDDict(), or
                                ZSTD_DCtx_refDDict() */
    U32 dictID;
    int ddictIsCold; /* if == 1 : dictionary is "new" for working context, and
                        presumed "cold" (not in cpu cache) */
    ZSTD_dictUses_e dictUses;

    /* streaming */
    ZSTD_dStreamStage streamStage;
    char* inBuff;
    size_t inBuffSize;
    size_t inPos;
    size_t maxWindowSize;
    char* outBuff;
    size_t outBuffSize;
    size_t outStart;
    size_t outEnd;
    size_t lhSize;
    void* legacyContext;
    U32 previousLegacyVersion;
    U32 legacyVersion;
    U32 hostageByte;
    int noForwardProgress;

    /* workspace */
    BYTE litBuffer[ZSTD_BLOCKSIZE_MAX + WILDCOPY_OVERLENGTH];
    BYTE headerBuffer[ZSTD_FRAMEHEADERSIZE_MAX];
}; /* typedef'd to ZSTD_DCtx within "zstd.h" */

/*-*******************************************************
 *  Shared internal functions
 *********************************************************/

/*! ZSTD_loadDEntropy() :
 *  dict : must point at beginning of a valid zstd dictionary.
 * @return : size of entropy tables read */
size_t ZSTD_loadDEntropy(ZSTD_entropyDTables_t* entropy, const void* const dict,
                         size_t const dictSize);

/*! ZSTD_checkContinuity() :
 *  check if next `dst` follows previous position, where decompression ended.
 *  If yes, do nothing (continue on current segment).
 *  If not, classify previous segment as "external dictionary", and start a new
 * segment. This function cannot fail. */
void ZSTD_checkContinuity(ZSTD_DCtx* dctx, const void* dst);

#endif /* ZSTD_DECOMPRESS_INTERNAL_H */
